Flight Data Sensors and Miscellaneous Components Flashcards
What can a layer of ice do to the aerodynamic characteristics of aircraft?
- Can reduce lift by 30%
- Increase drag by 40%
What can ice mean to the conditions for aerodynamic stall?
A/C may enter a stall before the stall warning activates
What are anti-icing systems?
Systems used to prevent the build up of ice on essential components and lifting surfaces, acting prior to entering icing conditions.
What are some forms of anti-icing systems?
- Pitot-static
- Angle of attack vanes
- Windscreens
- Engine intakes and engine components
- Wing and empennage leading edge surfaces
- Propeller
- Radome
Can be pneumatic, electrical or chemical
What are some forms of de-icing systems?
- De-icing systems are only activated after ice accretion has occurred.
- This is more energy efficient
- De-icing can be electrical, pneumatic, chemical, or mechanical.
What are some methods to determine icing conditions?
- Standing Instructions
- Aircraft Flight Manual
- Visual Detection
- Automatic detection (when icing conditions are encountered, A/C will prompt an alert)
Is the PC-21 approved for flight into icing conditions?
No
What are two thermal anti-icing de-icing systems?
- Bleed Air from Hot Compressor
2. Electrical Heaters
What are some common A/C components that use bleed air as anti-icing?
- Engine
2. A/C leading edge
What are some common A/C components that use electrical heating as anti-icing?
- Pitot probes
2. AOA probes
What are ground based spray equipment used for?
- Melt any ice and snow build up (de-ice) on the ground
2. Prevent the ice from re-forming until the aircraft is airborne (anti-ice)
What are some methods used to prevent windscreen anti-ice/de-ice?
1) Electrical heated windscreens that
Provide both anti-ice and de-ice
and Provide inner windscreen fog protection
2) Fluid systems such as rain repellent or chemical de-ice systems
3) Mechanical through rubber windscreen wipers
What are pneumatic windscreen systems used for?
Rain removal
What do the Air Speed Indicator (ASI), Vertical Speed Indicator (VSI) and Altimeter rely on?
- Air pressure in the atmosphere
- Change in air pressure is important as well
What are the ASI, VSI and Altimeter calibrated against?
ISA Conditions
What are ISA conditions?
T = 15 C P = 1013.25 hPa rho = 1.225 kg/m^3 ELR = -2/1000 ft -56.5 C @ 36,000 ft
What is static pressure?
Exerts equally in all directions, decreasing as altitude increases.
What is dynamic pressure? What factors determine it?
- Dynamic pressure is felt as relative movement between a body and the surrounding air.
- Air density and velocity
What is pitot pressure?
Static pressure + Dynamic pressure
How does a pressure altimeter work? How are they calibrated?
- Uses static ports on the A/C to determine aircraft height
- Changing static pressure will expand and contract aneroid barometers.
- Calibrated to ISA conditions
What are QNH and QFE? How can the pilot change the altimeter to be calibrated for these values?
- QNH = Actual sea level pressure
- QFE = Airfield level pressure
What is the PITHBLOT acronym used for? What are the letters stand for?
Altimeter errors:
- Position error
- Instrument error
- Temperature error
- Hysteresis error
- Barometric error
- Lag error
- Orographic effect
- Transonic jump
What are used as compensation devices to correct these errors?
Air Data Reference Units
What is position error?
Static source outside the A/C effected by airspeed configuration, sideslip or balance, power, steep turn, angle of attack
What is instrument error?
Caused by manufacturing tolerances
What is temperature error?
- Occurs when atmospheric conditions differ from the standard atmosphere calibration.
- In cold air masses, some corrections sometimes have to be made
What is hysteresis?
- An error associated with the imperfections of the aneroid capsule
- Friction or elasticity
What are barometric errors?
Errors caused by the difference between actual pressure and that to which the altimeter has been set
What are lag errors?
Errors due to the time it takes for mechanical devices to react to changes in pressure.
What are orographic errors?
Occurs when a current of air meets a hill or mountain.
What is a transonic jump?
Shockwaves momentarily increase static pressure during transonic flight.
What is typically regard as the most significant altimetry error?
Mis-setting of the correct barometric reference by the pilot.
What are regarded as the most significant instrument errors?
Temperature and barometric
How does the Airspeed Indicator (ASI) determine air speed?
Uses an aneroid capsule or diaphragm to measure the difference between static pressure and pitot pressure to determine dynamic pressure, which is proportional to the airspeed.
What causes some ASI errors?
- Density error - when density is not at ISA mean sea level
- Compressibility error - varies with speed and altitude, causes airspeed indicator to overread
- Position error (Pressure error) - Cause by changes in static pressure around the aircraft due to its movement through the air
- Instrument errors - caused by manufacturing tolerances
- Blockages in pitot or static ports
- Leaks in pitot or static ports
What does a VSI measure? How does it do it?
- Vertical Speed Indicator (Rate or descent/ascent per minute)
- Instrument contains a diaphragm or capsule inside a case
- When static pressure changes, the diaphragm or capsule moves immediately when a change in static pressure is detected while the pressure in the case lags.
- This difference results in the indication of vertical speed
What are the errors associated with VSI?
P = Position error I = Instrument error L = Lag T = Transonic jump Blockages
What is an Air Data Computer (ADC)?
Single computer system that can process pitot and static information and display them with a higher degree of accuracy.
What types of measurements does the ADC use to compensate for instrument errors?
- Temperature
- Angle of attack
- Aircraft Configuration
- Side slip angle
What forms of redundancy are displayed by the ADC?
- Multiple probes and ports provide information
- ADC monitors integrity of the probes and ports
- Standby instruments that can be used directly if the ADC fails